This invention relates to an X-ray computed tomography system (hereinafter referred to as an "X-ray CT system"). More particularly, the present invention relates to a system for obtaining a sectional image of an object the image of which is to be taken by irradiating an X-ray to the object, detecting the quantity of the transmitted X-ray, processing the detected signal by a computer or the like, and obtaining the sectional image, and specifically to the structure of an X-ray scanner for constituting the part which irradiates the X-ray to the object the image of which is to be taken, and detects the quantity of the transmitted X-ray.
In order to obtain a sectional image of an object the image of which is to be taken, an X-ray CT system needs an X-ray scanner which irradiates the X-rays to the object from a plurality of directions around the object and detects signals. The X-ray scanner in X-ray CT systems for medical diagnosis which has been used most widely at present disposes an X-ray source and a detector so as to face each other in an arc form and obtains signals from the peripheral direction of the object the image of which is to be taken, by rotating them unitarily and mechanically. (Refer, for example, to JP-B-1-45594.) Since the X-ray scanner is rotated mechanically, however, a rotating speed exceeding one turn per second cannot be obtained. Accordingly, dynamic imaging such as the motion of the heart, for example, cannot be made.
In order to solve this problem, an X-ray scanner which rotates electrically the X-ray source such as the one shown in FIG. 16 has been proposed (JP-A-60-12656). An anode target ring for the X-ray source and a plurality of detectors are shaped in the form of an arc and are fixed in such a manner as to face one another, an electron beam source is disposed at the apex of a cone using this circle has the bottom surface and an electron beam is scanned on the anode target ring for the X-ray source by deflection means so as to rotate the X-ray source. For this reason, mechanical rotation is not required. As a prior-art apparatus for similarly effecting high speed rotation, JP-A-61-68032 describes a method which deflects an electron beam in a circular trajectory inside a plane which is parallel to the sectional plane and irradiates the electron beam to an anode target ring for an X-ray source by a magnetic field.